This invention relates to a surface mount type semiconductor device usable as a diode, transistor and so on.
Up to now, surface mount type semiconductor devices have been proposed to be used as diodes, transistors and so on. One example of such semiconductor devices is shown in FIG. 16 to FIG. 18 of the accompanying drawings. The semiconductor device S may be a transistor, comprising an internal lead 91 as a base terminal, an internal lead 92 as a collector terminal, and an internal lead 93 as an emitter terminal.
The internal terminals 91, 92 and 93 are juxtaposed and are flush with one another. A substantially rectangular island 94 is formed at one end of the internal lead 91. A semiconductor chip 95 (also called a xe2x80x9cpelletxe2x80x9d) is die-bonded onto the island 94 using a gold wire W or the like, and is electrically connected to the internal leads 92 and 93. The semiconductor chip 95, gold wire W and internal leads 91-93 are housed in a resin package 97 made of thermosetting epoxy resin or the like. The internal leads 91 to 93 are folded and are respectively connected to external leads 11 to 13 on the outer surface of the resin package 97.
The semiconductor chip 95 generates heat as the semiconductor device S is operated. Especially, if the semiconductor device S is used as a power transistor, the generated heat should be efficiently radiated to the exterior of the resin package 97 in order to assure reliable operation of the semiconductor chip 95.
With the semiconductor device S, the semiconductor chip 95 is mounted on the island 94, which functions as a radiator for dissipating heat via the internal lead 91 or via the resin package 97 in contact with the internal lead 91. In this case, the island 94 preferably has a large upper surface area in order to promote heat radiation. Further, there has been a demand to enlarge the semiconductor chip 95 in order to improve the performance of electronic circuits integrated therein. Therefore, the island 94 is required to have a large upper surface area.
In order to increase the plane area of the island 94, it is conceivable to make the internal leads 92 and 93 juxtaposed on the island 94 smaller. However, both the island 94 and the internal leads 92 and 93 are positioned to be substantially flush with one another so that they are connected by gold wires W or the like. Naturally it is impossible to enlarge the island 94 without limit. At present, the upper surface area of the internal lead 91 occupies approximately 40% of the area of base of the resin package 97 at the most. As a result, it has been requested to increase the foregoing occupancy ratio in order to promote heat radiation.
It is an object of the invention to provide a semiconductor device which can overcome the foregoing problems of the related art or at least reduce those problems.
According to a first aspect of the invention, there is provided a semiconductor device comprising: a semiconductor chip; a chip-mounting internal lead having the semiconductor chip mounted thereon; chip-connecting internal leads which are electrically connected to an upper surface of the semiconductor chip; and a rectangular resin package which houses the semiconductor chip and the internal leads. In the semiconductor device, the chip-mounting internal lead includes one end which is rectangular or substantially rectangular along the length of the resin package.
An upper surface area of the chip-mounting lead is preferably equal to or larger than approximately 50% of an area of base of the resin package.
In this arrangement, the semiconductor device has a so-called wireless structure in which the chip-connecting internal leads are connected to the upper surface of the semiconductor chip on the chip-mounting internal lead. One end of the chip-mounting internal lead is rectangular or substantially rectangular along the length of the rectangular resin package. The upper surface area of the chip-mounting internal lead can be increased as desired. Therefore, heat generated by the semiconductor chip can be dissipated outward via the enlarged chip-mounting internal lead or via the resin package in contact with the chip-mounting internal lead. This improves the heat radiation of the semiconductor device. Further, the chip-connecting internal leads are directly connected to the semiconductor chip. For this reason it is possible to dissipate heat from the semiconductor chip through the chip-connecting internal leads, which contributes to improvement of heat radiation.
In a preferred embodiment of the invention, the semiconductor chip is mounted at the center of the chip-mounting internal lead extending along the length of the resin package.
In this arrangement, heat generated by the semiconductor chip is radiated widely along the length of the resin package (to the right and left) via the chip-mounting internal lead, compared with a case where the semiconductor chip is eccentrically mounted on the chip-mounting internal lead.
With a further preferred embodiment of the invention, a width of a non-end portion of the chip-mounting lead is equal to a width of the end.
This structure promotes heat radiation from the chip-mounting lead to the exterior.
According to a second aspect of the invention, there is provided a semiconductor device comprising: first and second semiconductor chips; first and second chip-mounting internal leads having the first and second semiconductor chips, respectively, mounted thereon; a plurality of chip-connecting internal leads which are electrically connected to upper surfaces of the first and second semiconductor chips; and a rectangular resin package housing the first and second semiconductor chips and the first and second internal leads. Each of the first and second chip-mounting internal leads includes one end which is rectangular or substantially rectangular along the length of the resin package.
It is preferable that an upper surface area of each end of the chip-mounting leads is equal to or larger than approximately 50% of an area of base of the resin package.
When a plurality of semiconductor chips are provided in the resin package, the chip-mounting internal leads for the semiconductor chips have ends thereof which are rectangular or substantially rectangular along the length of the resin package. The semiconductor device of the second aspect can have the wireless structure similarly to that of the first aspect. Therefore, the upper surface area of each end of the chip-mounting internal leads can occupy approximately 50% or more of the area of the base of the resin package. This is effective in dissipating heat generated by the semiconductor chips to the exterior of the semiconductor device.
In a still further embodiment, ends of the first and second chip-mounting internal leads are positioned to be flush with each other, so that the first and second semiconductor chips are juxtaposed in the resin package.
When a plurality of semiconductor chips are juxtaposed to be flush with one another, the semiconductor device can have a large upper surface area. However, the wireless structure effectively suppresses the enlargement of the upper surface area of the semiconductor device even when the semiconductor chips are juxtaposed in the resin package. This can substantially downsize the semiconductor device.
In a further embodiment of the invention, one end of either the first or second chip-connecting internal lead extends over the two upper surfaces of the first and second semiconductor chips, to thereby connect these upper surface together.
The ends of the chip-mounting internal leads are positioned to be flush with one another, which enables the semiconductor chips to be juxtaposed. This means that the upper surfaces of the semiconductor chips are positioned on the chip-mounting internal leads, so that the chip-connecting internal leads can extend over the upper surface of the semiconductor chips, and the upper surfaces of the semiconductor chips can be connected with one another. In other words, signal terminals of the semiconductor chips can be used in common, which is effective in reducing the number of external terminals of the semiconductor device. As a result, it is possible to reduce the component costs.
In a still further embodiment of the invention, the first and second semiconductor chips are positioned in the resin package with their upper surfaces facing in opposite directions. One end of the first chip-mounting internal lead is positioned near the bottom of the resin package while one end of the second chip-mounting internal lead is positioned near the upper part of the resin package.
The semiconductor chips are positioned with their upper surfaces facing in opposite directions, which means that the chip-mounting internal leads are longitudinally separated from each other in the resin package. This structure enables heat generated by the semiconductor chips to be more efficiently dissipated, compared with the structure in which the internal leads are eccentrically arranged in the resin package. Therefore, it is possible to improve radiation of heat generated by the semiconductor chips via the chip-mounting internal leads.
Other effects and advantages of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.